Method of surface finishing a metallic part



3,474,008 METHOD OF SURFACE FINISHING A METALLIC PART William J. Buisman, Amherst, Ohio, assignor to Standard Screw Company, Bellwood, Ill., a corporation of New .iersey No Drawing. Filed May 25, 1966, Ser. No. 552,702 lint. Cl. C23b 3/00, 5/50 US. Cl. 20433 7 Claims ABSTRACT OF THE DISCLOSURE A method of finishing metallic parts in which a random pattern may be etched onto the surface of the metallic part. In order to provide the desired pattern to be 1 etched on the part, a suitable masking material is sprayed toward the part in such a way that the masking fluid is slowly propelled from the source across a distance and onto the part. The spray fluid becomes a somewhat 0 This invention relates to a process for surface finishing metallic parts in which a random pattern may be etched into the metallic part and in which the etched and nonetched areas may receive desired contrasting finishes.

One purpose of the invention is a method of the type described which may be used for applying a decorative surface finish to chrome-plated plumbing parts.

Another purpose is a method of the type described which may be satisfactorily used on brass, copper or copper alloys of varied geometry and of varying initial finish.

Another purpose is a method of the type described in which the desired contrast between the etched and non-etched areas may be varied to provide diflerent finishing effects.

Other purposes will appear in the ensuing specification and claims.

The process disclosed herein can be used on brass, copper, copper alloys, or other metallic surfaces and on metallic parts having an infinite variety of geometric shapes. There may be an initial finish applied to the part, prior to the process described herein, and this initial finish can be a buffed finish, a polished finish, a stamped finish, or any other satisfactory finish, depending upon the ultimate tone of the finish desired on the particular part.

The first step in the process is to mask areas of the metallic part which are not to be subsequently etched. The masking may be done in a variety of patterns, and the invention is obviously not limited to any particular pattern of masking. Large areas may be masked. Small areas may be mask. The masking may be done in a random or in a planned pattern. A preferred method of masking is to apply, a masking material, in a random web type of pattern, by spraying a masking liquid onto the part.

As a specific example, a vinyl base masking material may be utilized. The masking fluid may be applied, under pressure, with a spray gun and a ten-pound atomizing pressure and eleven-pound fluid pressure has been found to be satisfactory. Preferably the spray patnite States Patent 0 tern is wide open and the gun is approximately five feet from the metallic part being sprayed. Such a combination results in a slow propelling of fluid across the distance between the gun and the part. The spray will be in a somewhat heavy irregular string of webbing fluid which reaches the part in a suitable stage of dryness and in a random, Windblown pattern. This pattern will appear as though a web has been laid about or on the metallic art.

p After the masking material has been applied to the part, the material is dried, preferably in an air-drying arrangement, for a time period not less than one-half hour. The drying time will depend upon the particular material used and the thickness to which the material is applied to the part.

After the masking material has been satisfactorily dried, the part is ready for etching in the areas which are exposed, The time of the application of the etching fluid and the strength of the etching fluid will depend upon the desired effect for the finished part. As a specific example of an etching solution, one gallon of fluid may contain 36 to 48 ounces of chromic acid, 8 to 11 fluid ounces of sulphuric acid, 66 B. and one fluid ounce of a wetting agent. The etching solution may be applied at a temperature of between 70 and degrees F. for a time period of from ten to fifteen minutes. Obviously the time period and the strength of the etching solution may be varied. Also, the ingredients of the solution will vary in accordance with the base metal.

After the part has been subjected to the etching solution for the time period desired, consistent with the depth of the etch desired, the part is subjected to a cold water rinse, and this may be either in the form of a bath or spray. In either type of rinse, it is desired to remove all of the etching solution from the part.

After the rinsing operation, for removing the etching solution, the mask can be removed from the part. Preferably the mask is removed by immersion in an alkaline solution, such as an electrocleaner for a period of approximately five minutes. The temperature of the alkaline solution may vary anywhere from room temperature to degrees F. Preferably the metallic part will act as a cathode in the mask removal solution and a direct current of from 20 to 40 amps per square ft. of solution may be applied. The application of this current, for the time period indicated, and in an alkaline solution as described, will result in the complete loosening of the sprayed mask of material. The masking material may then be either removed in the mask removal solution itself, or it may come off in subsequent rinses. In any event, once the metallic part is removed from the alkaline solution, it will be subjected to a number of rinses, which may be cold water or other satisfactory solutions, during which the remaining portions of the masking material will be removed.

Not only will the subsequent rinsing solutions remove the masking material, but they will also remove all of the alkaline solution from the metallic part so that it emerges from this stage of the operation as a clean metallic part with defined etched areas.

After the part has been etched, a two-stage toning effect may be applied, if desired. For example, the entire part may now be re-immersed in a chromic acid etch, as described above, for a period of time which is consistent with the desired tonal effect, for example 10-30 seconds. The application of the part into such an etching solution may apply some degree of etching to all areas. Duller areas, or duller etched areas of the part, may be toned up or brought up to a higher state of brightness by immersion in a chemical polishing solution for brass or copper. Such a solution may be utilized at full strength,

at room temperature, for a time period of -30 seconds.

After the toning operation described above, the parts are again rinsed and dried. The parts may be then plated in any satisfactory manner. They may be copper, nickel, or chrome-plated by standard procedures.

The final result of the process described above will be a plated part, which will have areas subdued in tone from the standard bright chrome finishes, and areas which are rich in tonal appearance. There may be a cobweb type of pattern on the finished part, or there may be larger or smaller defined areas. The pattern may be random or planned.

Whereas the preferred form of the invention has been shown and described herein, it should be realized that there are many modifications, substitutions and alterations thereto within the scope of the following claims.

I claim:

1. In a method of surface finishing a metallic part with defined etched areas including the steps of (a) slowly propelling a masking fluid from a source toward the metallic part which is in the area of about five feet from the source, the masking fluid being propelled from a source having an atomizing pressure in the area of about ten pounds and a fluid pressure in the area of about eleven pounds and with the spray pattern generally wide open such that the masking fluid is in the form of a heavy irregular string which is applied in a random windblown pattern upon the metallic part,

(b) drying the masking material,

(c) subjecting the masked part to an etching solution for a period of time consistent with the etch depth desired for the non-masked areas,

(d) rinsing the part to remove the etching solution,

(e) thereafter removing the masking material by subjecting the part to a rinsing solution for a period of time suflicient to completely remove the masking material from the part,

(f) then finishing the part to provide the desired contrast between the etched and non-etched areas.

2. The method of claim 1 further characterized by and including the initial step of applying a finish to the metallic part, prior to the masking step.

3. The method of claim 1 further characterized in that the masking fluid is a vinyl base material.

4. The method of claim 1 further characterized in that the masking material is air dried for a period of at least one-half hour.

5. The method of claim 1 further characterized in that the etching solution includes chromic acid, sulphuric acid and a Wetting agent, and is applied for a time period of between ten and fifteen minutes and at a temperature of -120 degrees F.

'6. The method of claim 1 further characterized in that the etching solution is removed by a cold water rinse.

7. The method of claim 1 further characterized in that the masking material is removed by immersing the part in an alkaline solution in which a direct current is applied to the solution and the metallic part functions as the cathode.

References Cited UNITED STATES PATENTS 2,708,655 5/1955 Turner 204-1405 3,037,896 6/1962 Gauntt et a1. 156l3 3,052,957 9/1962 Swanson 204-15 3,079,352 2/1963 Atkins et al. 2603.5 3,206,342 9/1965 Briggs 204143 XR JOHN H. MACK, Primary Examiner W. B. VANSISE, Assistant Examiner US. Cl. X.R. 

